To complete a well, one or more formation zones adjacent a wellbore are perforated to allow fluid from the formation zones to flow into the well for production to the surface or to allow injection fluids to be applied into the formation zones. A perforating gun string may be lowered into the well and the guns fired to create openings in casing and to extend perforations into the surrounding formation.
When the shaped charge is detonated a portion of the liner forms a jet portion of the liner. The jet is propelled away from the jacket in a direction toward a target. Another portion of the liner is propelled away from the jacket and forms what is known as a slug or carrot portion of the liner. The slug or carrot portion is not propelled to the same extent as the “jet”. When the shaped charge is used in a perforating gun, the target is normally a cased downhole formation. Upon detonation, the jet portion of the liner is propelled through the casing and penetrates the downhole formation to enhance recovery of downhole hydrocarbons. The slug portion, on the other hand, is designed to break up upon contact with the casing.
The explosive nature of the formation of perforation tunnels shatters sand grains of the formation. A layer of “shock damaged region” having a permeability lower than that of the virgin formation matrix may be formed around each perforation tunnel. The process may also generate a tunnel full of rock debris mixed in with the perforator charge debris. The extent of the damage, and the amount of loose debris in the tunnel, may be dictated by a variety of factors including formation properties, explosive charge properties, pressure conditions, fluid properties, and so forth. The shock damaged region and loose debris in the perforation tunnels may impair the productivity of production wells or the injectivity of injector wells.
In connection with those and other issues, there is continued need to improve the overall performance of perforating and perforating guns in many aspects. The present application addresses a number of present needs in that area.